1. Field of the Invention
The present invention illustrates a projector and more particularly, the projector with a two-axis tilting digital micro-mirror device and low light leakage effect.
2. Description of the Prior Art
The conventional projector can project micro-images to a huge screen by a digital micro-mirror device (DMD). Further, since the conventional projector provides sufficient brightness, the image data can be displayed and then shared to everyone.
FIG. 1 illustrates a structure of a conventional projector 50. As shown in FIG. 1, the conventional projector 50 includes a digital micro-mirror device 10, a total internal reflection (TIR) prism set 11, a reflecting mirror (reflector) 12, a lens module 13, and a light pipe 14. For illustrating viewing direction explicitly, 3 perpendicular axes of Cartesian coordinates are represented on the right hand side in FIG. 1. Specifically, the viewing direction on X-axis is a direction from an origin point to the right side. The viewing direction on Y-axis is a direction from the origin point to the underside. The viewing direction on Z-axis is an incident direction on X-Y plane. In the conventional projector 50, an incident light passes the lens module 13 through the light pipe 14 and is reflected to the TIR prism set 11 by the reflecting mirror 12. Finally, the incident light is reflected as an image light by the digital micro-mirror device 10 and then projected to the screen. However, the digital micro-mirror device 10 can only receive the incident light with oblique incident direction because of the physical limitation of the digital micro-mirror device 10. Thus, the disposition between the TIR prism set 11 and the digital micro-mirror device 10 introduces an inclination angle (i.e., such as 45 degrees of angle). As a result, the volume of the conventional projector 50 is bounded by the inclination angle. Since the volume reduction is the major issue of the projector design, the conventional projector 50 with big volume becomes inconvenient and thereby losses of competitiveness.
Besides, when the digital micro-mirror device 10 of the projector 50 is operated in OFF-state, a leakage light of the image light may be reflected to the projector 50 back inside the TIR prism set 11. As a result, the effect of scattering reflection and diffuse reflection is introduced, especially in a cusp, gluing, or edge of the prisms. The effect of scattering reflection and diffuse reflection reduces contrast and quality of image display.
Thus, to develop a projector with small volume and low light leakage effect is important.